PHP Lesson 3: Databases, File Handling & Object-Oriented Programming

MA Hussain

Oct 31, 2025 - 11:44

0 133736

PHP Lesson 3: Databases, File Handling & Object-Oriented Programming

Welcome to Lesson 3! Now we're moving into more advanced PHP concepts that will let you build robust, real-world applications.

Part 1: MySQL Database Integration

1.1 Setting Up Database Connection

First, let's create a proper database connection class:

<?php
class Database {
    private $host = 'localhost';
    private $db_name = 'php_app';
    private $username = 'root';
    private $password = '';
    private $conn;
    
    public function connect() {
        $this->conn = null;
        
        try {
            $this->conn = new PDO(
                "mysql:host=" . $this->host . ";dbname=" . $this->db_name,
                $this->username,
                $this->password
            );
            $this->conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            $this->conn->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
        } catch(PDOException $e) {
            echo "Connection Error: " . $e->getMessage();
        }
        
        return $this->conn;
    }
}

// Create database and table setup script (run once)
function setupDatabase() {
    try {
        $temp_conn = new PDO("mysql:host=localhost", "root", "");
        $temp_conn->exec("CREATE DATABASE IF NOT EXISTS php_app");
        $temp_conn->exec("USE php_app");
        
        $sql = "CREATE TABLE IF NOT EXISTS users (
            id INT AUTO_INCREMENT PRIMARY KEY,
            name VARCHAR(100) NOT NULL,
            email VARCHAR(100) UNIQUE NOT NULL,
            password VARCHAR(255) NOT NULL,
            role ENUM('user', 'admin') DEFAULT 'user',
            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
        )";
        $temp_conn->exec($sql);
        
        $sql = "CREATE TABLE IF NOT EXISTS posts (
            id INT AUTO_INCREMENT PRIMARY KEY,
            title VARCHAR(255) NOT NULL,
            content TEXT NOT NULL,
            user_id INT,
            image_path VARCHAR(255),
            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
            updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
            FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE
        )";
        $temp_conn->exec($sql);
        
        // Insert sample data
        $temp_conn->exec("INSERT IGNORE INTO users (name, email, password, role) VALUES 
            ('Admin User', 'admin@example.com', '" . password_hash('admin123', PASSWORD_DEFAULT) . "', 'admin'),
            ('John Doe', 'john@example.com', '" . password_hash('password123', PASSWORD_DEFAULT) . "', 'user')
        ");
        
        echo "Database setup completed successfully!";
        
    } catch(PDOException $e) {
        echo "Setup Error: " . $e->getMessage();
    }
}

// Uncomment the line below to run setup (run once only)
// setupDatabase();
?>

1.2 User Registration & Login System with Database

<?php
session_start();
require_once 'Database.php';

class User {
    private $db;
    private $table = 'users';
    
    public function __construct() {
        $database = new Database();
        $this->db = $database->connect();
    }
    
    // Register new user
    public function register($name, $email, $password) {
        try {
            // Check if email already exists
            $query = "SELECT id FROM " . $this->table . " WHERE email = :email";
            $stmt = $this->db->prepare($query);
            $stmt->bindParam(':email', $email);
            $stmt->execute();
            
            if ($stmt->rowCount() > 0) {
                return "Email already exists!";
            }
            
            // Insert new user
            $query = "INSERT INTO " . $this->table . " (name, email, password) VALUES (:name, :email, :password)";
            $stmt = $this->db->prepare($query);
            
            $hashed_password = password_hash($password, PASSWORD_DEFAULT);
            
            $stmt->bindParam(':name', $name);
            $stmt->bindParam(':email', $email);
            $stmt->bindParam(':password', $hashed_password);
            
            if ($stmt->execute()) {
                return true;
            }
            
        } catch(PDOException $e) {
            return "Error: " . $e->getMessage();
        }
    }
    
    // Login user
    public function login($email, $password) {
        try {
            $query = "SELECT * FROM " . $this->table . " WHERE email = :email";
            $stmt = $this->db->prepare($query);
            $stmt->bindParam(':email', $email);
            $stmt->execute();
            
            if ($stmt->rowCount() == 1) {
                $user = $stmt->fetch();
                
                if (password_verify($password, $user['password'])) {
                    $_SESSION['user_id'] = $user['id'];
                    $_SESSION['user_name'] = $user['name'];
                    $_SESSION['user_role'] = $user['role'];
                    return true;
                }
            }
            
            return "Invalid email or password!";
            
        } catch(PDOException $e) {
            return "Error: " . $e->getMessage();
        }
    }
    
    // Get user by ID
    public function getUserById($id) {
        try {
            $query = "SELECT id, name, email, role, created_at FROM " . $this->table . " WHERE id = :id";
            $stmt = $this->db->prepare($query);
            $stmt->bindParam(':id', $id);
            $stmt->execute();
            
            return $stmt->fetch();
            
        } catch(PDOException $e) {
            return null;
        }
    }
}

// Handle form submissions
$user = new User();
$message = '';

if (isset($_POST['register'])) {
    $result = $user->register($_POST['name'], $_POST['email'], $_POST['password']);
    if ($result === true) {
        $message = "Registration successful! Please login.";
    } else {
        $message = $result;
    }
}

if (isset($_POST['login'])) {
    $result = $user->login($_POST['email'], $_POST['password']);
    if ($result === true) {
        header("Location: dashboard.php");
        exit();
    } else {
        $message = $result;
    }
}
?>

<!DOCTYPE html>
<html>
<head>
    <title>User Authentication</title>
    <style>
        body { font-family: Arial, sans-serif; max-width: 800px; margin: 50px auto; padding: 20px; }
        .container { display: grid; grid-template-columns: 1fr 1fr; gap: 40px; }
        .form-section { background: #f8f9fa; padding: 30px; border-radius: 10px; }
        .form-group { margin-bottom: 20px; }
        label { display: block; margin-bottom: 5px; font-weight: bold; }
        input { width: 100%; padding: 12px; border: 1px solid #ddd; border-radius: 5px; box-sizing: border-box; }
        button { background: #007bff; color: white; padding: 12px 30px; border: none; border-radius: 5px; cursor: pointer; }
        button:hover { background: #0056b3; }
        .message { padding: 15px; margin-bottom: 20px; border-radius: 5px; }
        .success { background: #d4edda; color: #155724; }
        .error { background: #f8d7da; color: #721c24; }
    </style>
</head>
<body>
    <h1>User Authentication System</h1>
    
    <?php if ($message): ?>
        <div class="message <?= strpos($message, 'successful') !== false ? 'success' : 'error' ?>">
            <?= $message ?>
        </div>
    <?php endif; ?>
    
    <div class="container">
        <!-- Registration Form -->
        <div class="form-section">
            <h2>Register</h2>
            <form method="POST">
                <div class="form-group">
                    <label>Full Name</label>
                    <input type="text" name="name" required>
                </div>
                <div class="form-group">
                    <label>Email</label>
                    <input type="email" name="email" required>
                </div>
                <div class="form-group">
                    <label>Password</label>
                    <input type="password" name="password" required minlength="6">
                </div>
                <button type="submit" name="register">Register</button>
            </form>
        </div>
        
        <!-- Login Form -->
        <div class="form-section">
            <h2>Login</h2>
            <form method="POST">
                <div class="form-group">
                    <label>Email</label>
                    <input type="email" name="email" required>
                </div>
                <div class="form-group">
                    <label>Password</label>
                    <input type="password" name="password" required>
                </div>
                <button type="submit" name="login">Login</button>
            </form>
        </div>
    </div>
</body>
</html>

Part 2: File Uploads and Handling

2.1 Advanced File Upload System

<?php
class FileManager {
    private $uploadDir = 'uploads/';
    private $allowedTypes = ['jpg', 'jpeg', 'png', 'gif', 'pdf', 'txt'];
    private $maxSize = 5 * 1024 * 1024; // 5MB
    
    public function __construct() {
        // Create upload directory if it doesn't exist
        if (!file_exists($this->uploadDir)) {
            mkdir($this->uploadDir, 0777, true);
        }
    }
    
    public function uploadFile($file) {
        $errors = [];
        $filePath = '';
        
        if ($file['error'] === UPLOAD_ERR_OK) {
            $fileName = $file['name'];
            $fileTmp = $file['tmp_name'];
            $fileSize = $file['size'];
            $fileExt = strtolower(pathinfo($fileName, PATHINFO_EXTENSION));
            
            // Generate unique filename
            $newFileName = uniqid() . '_' . time() . '.' . $fileExt;
            $filePath = $this->uploadDir . $newFileName;
            
            // Validate file type
            if (!in_array($fileExt, $this->allowedTypes)) {
                $errors[] = "File type not allowed. Allowed types: " . implode(', ', $this->allowedTypes);
            }
            
            // Validate file size
            if ($fileSize > $this->maxSize) {
                $errors[] = "File too large. Maximum size: " . ($this->maxSize / 1024 / 1024) . "MB";
            }
            
            // Move file if no errors
            if (empty($errors)) {
                if (move_uploaded_file($fileTmp, $filePath)) {
                    return [
                        'success' => true,
                        'file_path' => $filePath,
                        'file_name' => $fileName,
                        'file_size' => $fileSize
                    ];
                } else {
                    $errors[] = "Failed to upload file.";
                }
            }
        } else {
            $errors[] = "Upload error: " . $this->getUploadError($file['error']);
        }
        
        return [
            'success' => false,
            'errors' => $errors
        ];
    }
    
    public function getUploadedFiles() {
        $files = [];
        if (is_dir($this->uploadDir)) {
            $fileList = scandir($this->uploadDir);
            foreach ($fileList as $file) {
                if ($file !== '.' && $file !== '..') {
                    $filePath = $this->uploadDir . $file;
                    $files[] = [
                        'name' => $file,
                        'path' => $filePath,
                        'size' => filesize($filePath),
                        'modified' => filemtime($filePath)
                    ];
                }
            }
        }
        return $files;
    }
    
    public function deleteFile($fileName) {
        $filePath = $this->uploadDir . $fileName;
        if (file_exists($filePath) && is_file($filePath)) {
            return unlink($filePath);
        }
        return false;
    }
    
    private function getUploadError($errorCode) {
        $errors = [
            UPLOAD_ERR_INI_SIZE => 'File exceeds upload_max_filesize directive',
            UPLOAD_ERR_FORM_SIZE => 'File exceeds MAX_FILE_SIZE directive',
            UPLOAD_ERR_PARTIAL => 'File was only partially uploaded',
            UPLOAD_ERR_NO_FILE => 'No file was uploaded',
            UPLOAD_ERR_NO_TMP_DIR => 'Missing temporary folder',
            UPLOAD_ERR_CANT_WRITE => 'Failed to write file to disk',
            UPLOAD_ERR_EXTENSION => 'A PHP extension stopped the file upload'
        ];
        return $errors[$errorCode] ?? 'Unknown upload error';
    }
}

// Handle file operations
$fileManager = new FileManager();
$message = '';

if (isset($_POST['upload'])) {
    $result = $fileManager->uploadFile($_FILES['file']);
    if ($result['success']) {
        $message = "File uploaded successfully!";
    } else {
        $message = "Upload failed: " . implode(', ', $result['errors']);
    }
}

if (isset($_GET['delete'])) {
    if ($fileManager->deleteFile($_GET['delete'])) {
        $message = "File deleted successfully!";
    } else {
        $message = "Failed to delete file!";
    }
    header("Location: " . str_replace('&delete=' . $_GET['delete'], '', $_SERVER['REQUEST_URI']));
    exit();
}

$uploadedFiles = $fileManager->getUploadedFiles();
?>

<!DOCTYPE html>
<html>
<head>
    <title>File Manager</title>
    <style>
        body { font-family: Arial, sans-serif; max-width: 1000px; margin: 0 auto; padding: 20px; }
        .container { display: grid; grid-template-columns: 1fr 2fr; gap: 30px; }
        .section { background: #f8f9fa; padding: 25px; border-radius: 10px; }
        .file-list { max-height: 500px; overflow-y: auto; }
        .file-item { background: white; padding: 15px; margin: 10px 0; border-radius: 5px; display: flex; justify-content: space-between; align-items: center; }
        .file-info { flex-grow: 1; }
        .file-actions a { margin-left: 10px; text-decoration: none; padding: 5px 10px; border-radius: 3px; }
        .delete-btn { background: #dc3545; color: white; }
        .view-btn { background: #007bff; color: white; }
        .message { padding: 15px; margin-bottom: 20px; border-radius: 5px; }
        .success { background: #d4edda; color: #155724; }
        .error { background: #f8d7da; color: #721c24; }
    </style>
</head>
<body>
    <h1>File Management System</h1>
    
    <?php if ($message): ?>
        <div class="message <?= strpos($message, 'successfully') !== false ? 'success' : 'error' ?>">
            <?= $message ?>
        </div>
    <?php endif; ?>
    
    <div class="container">
        <!-- Upload Section -->
        <div class="section">
            <h2>Upload File</h2>
            <form method="POST" enctype="multipart/form-data">
                <div style="margin-bottom: 20px;">
                    <input type="file" name="file" required style="padding: 10px;">
                </div>
                <button type="submit" name="upload">Upload File</button>
            </form>
            
            <div style="margin-top: 20px; padding: 15px; background: #e9ecef; border-radius: 5px;">
                <h3>Upload Guidelines:</h3>
                <ul>
                    <li>Maximum file size: 5MB</li>
                    <li>Allowed types: JPG, JPEG, PNG, GIF, PDF, TXT</li>
                    <li>Files are renamed for security</li>
                </ul>
            </div>
        </div>
        
        <!-- File List Section -->
        <div class="section">
            <h2>Uploaded Files (<?= count($uploadedFiles) ?>)</h2>
            <div class="file-list">
                <?php if (empty($uploadedFiles)): ?>
                    <p>No files uploaded yet.</p>
                <?php else: ?>
                    <?php foreach($uploadedFiles as $file): ?>
                        <div class="file-item">
                            <div class="file-info">
                                <strong><?= $file['name'] ?></strong><br>
                                <small>Size: <?= round($file['size'] / 1024, 2) ?> KB</small><br>
                                <small>Modified: <?= date('Y-m-d H:i', $file['modified']) ?></small>
                            </div>
                            <div class="file-actions">
                                <a href="<?= $file['path'] ?>" class="view-btn" target="_blank">View</a>
                                <a href="?delete=<?= $file['name'] ?>" class="delete-btn" 
                                   onclick="return confirm('Delete this file?')">Delete</a>
                            </div>
                        </div>
                    <?php endforeach; ?>
                <?php endif; ?>
            </div>
        </div>
    </div>
</body>
</html>

Part 3: Object-Oriented PHP - Blog System

3.1 Complete Blog System with OOP

<?php
session_start();
require_once 'Database.php';

class Post {
    private $db;
    private $table = 'posts';
    
    public function __construct() {
        $database = new Database();
        $this->db = $database->connect();
    }
    
    // Create new post
    public function create($title, $content, $userId, $imagePath = null) {
        try {
            $query = "INSERT INTO " . $this->table . " (title, content, user_id, image_path) 
                     VALUES (:title, :content, :user_id, :image_path)";
            $stmt = $this->db->prepare($query);
            
            $stmt->bindParam(':title', $title);
            $stmt->bindParam(':content', $content);
            $stmt->bindParam(':user_id', $userId);
            $stmt->bindParam(':image_path', $imagePath);
            
            return $stmt->execute();
            
        } catch(PDOException $e) {
            return false;
        }
    }
    
    // Get all posts with user information
    public function getAll() {
        try {
            $query = "SELECT p.*, u.name as author_name 
                     FROM " . $this->table . " p 
                     LEFT JOIN users u ON p.user_id = u.id 
                     ORDER BY p.created_at DESC";
            $stmt = $this->db->prepare($query);
            $stmt->execute();
            
            return $stmt->fetchAll();
            
        } catch(PDOException $e) {
            return [];
        }
    }
    
    // Get single post by ID
    public function getById($id) {
        try {
            $query = "SELECT p.*, u.name as author_name 
                     FROM " . $this->table . " p 
                     LEFT JOIN users u ON p.user_id = u.id 
                     WHERE p.id = :id";
            $stmt = $this->db->prepare($query);
            $stmt->bindParam(':id', $id);
            $stmt->execute();
            
            return $stmt->fetch();
            
        } catch(PDOException $e) {
            return null;
        }
    }
    
    // Update post
    public function update($id, $title, $content, $imagePath = null) {
        try {
            $query = "UPDATE " . $this->table . " 
                     SET title = :title, content = :content, image_path = :image_path 
                     WHERE id = :id";
            $stmt = $this->db->prepare($query);
            
            $stmt->bindParam(':id', $id);
            $stmt->bindParam(':title', $title);
            $stmt->bindParam(':content', $content);
            $stmt->bindParam(':image_path', $imagePath);
            
            return $stmt->execute();
            
        } catch(PDOException $e) {
            return false;
        }
    }
    
    // Delete post
    public function delete($id) {
        try {
            $query = "DELETE FROM " . $this->table . " WHERE id = :id";
            $stmt = $this->db->prepare($query);
            $stmt->bindParam(':id', $id);
            
            return $stmt->execute();
            
        } catch(PDOException $e) {
            return false;
        }
    }
}

class BlogSystem {
    private $post;
    private $fileManager;
    
    public function __construct() {
        $this->post = new Post();
        $this->fileManager = new FileManager();
    }
    
    public function handleRequest() {
        $action = $_POST['action'] ?? $_GET['action'] ?? '';
        $message = '';
        
        switch ($action) {
            case 'create':
                if (isset($_SESSION['user_id'])) {
                    $imagePath = null;
                    
                    // Handle file upload
                    if (!empty($_FILES['image']['name'])) {
                        $uploadResult = $this->fileManager->uploadFile($_FILES['image']);
                        if ($uploadResult['success']) {
                            $imagePath = $uploadResult['file_path'];
                        }
                    }
                    
                    if ($this->post->create($_POST['title'], $_POST['content'], $_SESSION['user_id'], $imagePath)) {
                        $message = "Post created successfully!";
                    } else {
                        $message = "Failed to create post!";
                    }
                }
                break;
                
            case 'delete':
                if (isset($_SESSION['user_id'])) {
                    $post = $this->post->getById($_POST['post_id']);
                    // Check if user owns the post or is admin
                    if ($post && ($post['user_id'] == $_SESSION['user_id'] || $_SESSION['user_role'] == 'admin')) {
                        if ($this->post->delete($_POST['post_id'])) {
                            $message = "Post deleted successfully!";
                        }
                    }
                }
                break;
        }
        
        return $message;
    }
    
    public function getAllPosts() {
        return $this->post->getAll();
    }
}

// Initialize blog system
$blogSystem = new BlogSystem();
$message = $blogSystem->handleRequest();
$posts = $blogSystem->getAllPosts();
?>

<!DOCTYPE html>
<html>
<head>
    <title>PHP Blog System</title>
    <style>
        body { font-family: Arial, sans-serif; max-width: 1200px; margin: 0 auto; padding: 20px; background: #f5f5f5; }
        .container { display: grid; grid-template-columns: 1fr 2fr; gap: 30px; }
        .section { background: white; padding: 25px; border-radius: 10px; box-shadow: 0 2px 10px rgba(0,0,0,0.1); }
        .post-form input, .post-form textarea { width: 100%; padding: 12px; margin: 8px 0; border: 1px solid #ddd; border-radius: 5px; box-sizing: border-box; }
        .post-form textarea { height: 150px; resize: vertical; }
        .post-item { background: white; padding: 20px; margin: 15px 0; border-radius: 8px; border-left: 4px solid #007bff; }
        .post-title { color: #333; margin: 0 0 10px 0; }
        .post-meta { color: #666; font-size: 0.9em; margin-bottom: 15px; }
        .post-content { line-height: 1.6; margin-bottom: 15px; }
        .post-image { max-width: 100%; height: auto; border-radius: 5px; margin: 10px 0; }
        .btn { padding: 10px 20px; border: none; border-radius: 5px; cursor: pointer; text-decoration: none; display: inline-block; }
        .btn-primary { background: #007bff; color: white; }
        .btn-danger { background: #dc3545; color: white; }
        .message { padding: 15px; margin-bottom: 20px; border-radius: 5px; }
        .success { background: #d4edda; color: #155724; }
        .error { background: #f8d7da; color: #721c24; }
    </style>
</head>
<body>
    <h1>PHP Blog System</h1>
    
    <?php if ($message): ?>
        <div class="message <?= strpos($message, 'successfully') !== false ? 'success' : 'error' ?>">
            <?= $message ?>
        </div>
    <?php endif; ?>
    
    <div class="container">
        <!-- Create Post Form -->
        <?php if (isset($_SESSION['user_id'])): ?>
        <div class="section">
            <h2>Create New Post</h2>
            <form method="POST" enctype="multipart/form-data" class="post-form">
                <input type="hidden" name="action" value="create">
                
                <div>
                    <label>Post Title</label>
                    <input type="text" name="title" required>
                </div>
                
                <div>
                    <label>Content</label>
                    <textarea name="content" required></textarea>
                </div>
                
                <div>
                    <label>Featured Image (Optional)</label>
                    <input type="file" name="image" accept="image/*">
                </div>
                
                <button type="submit" class="btn btn-primary">Publish Post</button>
            </form>
        </div>
        <?php else: ?>
        <div class="section">
            <h2>Welcome to Our Blog</h2>
            <p>Please <a href="auth.php">login</a> to create posts.</p>
        </div>
        <?php endif; ?>
        
        <!-- Blog Posts -->
        <div class="section">
            <h2>Latest Posts</h2>
            
            <?php if (empty($posts)): ?>
                <p>No posts yet. Be the first to post!</p>
            <?php else: ?>
                <?php foreach($posts as $post): ?>
                    <div class="post-item">
                        <h3 class="post-title"><?= htmlspecialchars($post['title']) ?></h3>
                        <div class="post-meta">
                            By <?= htmlspecialchars($post['author_name']) ?> | 
                            <?= date('F j, Y g:i A', strtotime($post['created_at'])) ?>
                            <?php if ($post['updated_at'] != $post['created_at']): ?>
                                | Updated: <?= date('F j, Y g:i A', strtotime($post['updated_at'])) ?>
                            <?php endif; ?>
                        </div>
                        
                        <?php if ($post['image_path']): ?>
                            <img src="<?= $post['image_path'] ?>" alt="Post image" class="post-image">
                        <?php endif; ?>
                        
                        <div class="post-content">
                            <?= nl2br(htmlspecialchars($post['content'])) ?>
                        </div>
                        
                        <?php if (isset($_SESSION['user_id']) && ($_SESSION['user_id'] == $post['user_id'] || $_SESSION['user_role'] == 'admin')): ?>
                            <form method="POST" style="display: inline;">
                                <input type="hidden" name="action" value="delete">
                                <input type="hidden" name="post_id" value="<?= $post['id'] ?>">
                                <button type="submit" class="btn btn-danger" 
                                        onclick="return confirm('Delete this post?')">Delete</button>
                            </form>
                        <?php endif; ?>
                    </div>
                <?php endforeach; ?>
            <?php endif; ?>
        </div>
    </div>
</body>
</html>

Part 4: Dashboard for Logged-in Users

4.1 User Dashboard

<?php
// dashboard.php
session_start();
require_once 'Database.php';

if (!isset($_SESSION['user_id'])) {
    header("Location: auth.php");
    exit();
}

$user = new User();
$currentUser = $user->getUserById($_SESSION['user_id']);
?>

<!DOCTYPE html>
<html>
<head>
    <title>Dashboard</title>
    <style>
        body { font-family: Arial, sans-serif; max-width: 1200px; margin: 0 auto; padding: 20px; }
        .header { background: #007bff; color: white; padding: 20px; border-radius: 10px; margin-bottom: 30px; }
        .nav { background: #f8f9fa; padding: 15px; border-radius: 5px; margin-bottom: 20px; }
        .nav a { margin-right: 15px; text-decoration: none; color: #007bff; }
        .stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; margin-bottom: 30px; }
        .stat-card { background: white; padding: 20px; border-radius: 8px; text-align: center; box-shadow: 0 2px 5px rgba(0,0,0,0.1); }
    </style>
</head>
<body>
    <div class="header">
        <h1>Welcome, <?= $currentUser['name'] ?>!</h1>
        <p>Role: <?= ucfirst($currentUser['role']) ?> | Member since: <?= date('F Y', strtotime($currentUser['created_at'])) ?></p>
    </div>
    
    <div class="nav">
        <a href="blog.php">Blog</a>
        <a href="file_manager.php">File Manager</a>
        <a href="logout.php">Logout</a>
    </div>
    
    <div class="stats">
        <div class="stat-card">
            <h3>Blog Posts</h3>
            <p>12</p>
        </div>
        <div class="stat-card">
            <h3>Files Uploaded</h3>
            <p>8</p>
        </div>
        <div class="stat-card">
            <h3>Comments</h3>
            <p>23</p>
        </div>
    </div>
    
    <h2>Quick Actions</h2>
    <div class="stats">
        <div class="stat-card">
            <h4>Write New Post</h4>
            <a href="blog.php" class="btn btn-primary">Create Post</a>
        </div>
        <div class="stat-card">
            <h4>Upload Files</h4>
            <a href="file_manager.php" class="btn btn-primary">Upload</a>
        </div>
        <div class="stat-card">
            <h4>Manage Profile</h4>
            <a href="profile.php" class="btn btn-primary">Profile</a>
        </div>
    </div>
</body>
</html>

Key Concepts Covered:

Database Integration: PDO, prepared statements, relationships
File Handling: Upload, validation, management
Object-Oriented Programming: Classes, methods, encapsulation
Session Management: User authentication and authorization
Security: SQL injection prevention, file type validation
Error Handling: Try-catch blocks, user-friendly messages

Practice Exercises:

Add a comment system to the blog
Implement user profile editing
Create an admin panel for user management
Add pagination to the blog posts
Implement image resizing for uploaded images

Next Lesson Preview:

In Lesson 4, we'll cover:

RESTful APIs with PHP
AJAX integration
Email sending
Payment gateway integration
Building a complete e-commerce system

You've now built a complete web application with database integration, file handling, and object-oriented programming! These are the skills used in real-world PHP development.

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PHP Next Lesson: Working with Data - Arrays, Functions, and Forms

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PHP Lesson 3: Databases, File Handling & Object-Oriented Programming

PHP Lesson 3: Databases, File Handling & Object-Oriented Programming

Part 1: MySQL Database Integration

1.1 Setting Up Database Connection

1.2 User Registration & Login System with Database

Part 2: File Uploads and Handling

2.1 Advanced File Upload System

Part 3: Object-Oriented PHP - Blog System

3.1 Complete Blog System with OOP

Part 4: Dashboard for Logged-in Users

4.1 User Dashboard

Key Concepts Covered:

Practice Exercises:

Next Lesson Preview:

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